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Since the early 1980s, shock wave treatment has been the golden standard treatment option for the disintegration of kidney stones in urology. A wide range of beneficial effects of shock waves on the human body was soon identified, starting with first observations of bone densification at the iliac crest after treatment of kidney stones. Since then, the indications for shock wave therapy have conquered areas apart from the field of urology. Nowadays, shock wave therapy is used for a variety of indications such as tendinopathies or impaired bone healing.
Furthermore, patients suffering from poor wound healing such as diabetic foot ulcers and also chronic, non-healing wounds are treated successfully with shock waves. Despite the versatile application fields of shock wave therapy, the general principles underlying the beneficial effect of this treatment still remain to be fully elucidated. Several in vitro and in vivo studies, mostly involving osteoblast like cells and the osteo-inductive potential of shock wave treatment, already highlighted the role of the activation of mechanotransductory signaling pathways. For the clinical application of shock wave therapy as an accepted treatment for critically healing wounds (e.g. chronic or diabetic wounds, burns), general mechanistic evidence to explain the underlying mechanisms is essential. These data would facilitate the standardized application of this non-invasive, cost efficient and low- risk bearing therapy, which can be performed in an outpatient setting.
First of all, an in vitro set-up was established and the necessary technical parameters for the optimal application of shock wave treatment on cell cultures were defined in this thesis. For this purpose, a molecule uptake assay was used as a functional assay. The following aims of this study were to elucidate the effect of shock wave treatment on intracellular signaling in vitro and to ultimately describe their role in the wound healing effect of shock wave treatment in vivo. To identify universal effects of shock wave treatment on intracellular signaling mechanisms, various cell lines were used, including the human U937 monocytic cell line, a human Jurkat T-cell line, the human MG63 osteosarcoma cell line, the C3H10T1/2 mouse mesenchymal progenitor cell line as well as primary human peripheral mononuclear cells. For the first time, the affected signaling cascade leading to the proliferative effect of shock wave treatment in vitro was described in detail in mouse C3H10T1/2 cells as well as in human adipose tissue-derived stem cells and human Jurkat T-cells. Further, ATP release from shock wave treated cells was shown to initiate intracellular Erk1/2 signaling activation via purinergic signaling. The thereby ultimately increased proliferation was reported to be dependent on shock wave treatment triggered Erk1/2 pathway activation. An in vivo study on impaired wound healing in rats confirmed the hypothesis on the essential role of Erk1/2 signaling in the shock wave treatment induced wound healing effect. Data clearly indicate the crucial importance of the Erk1/2 signaling cascade in the proliferative and wound healing effect of shock wave treatment.
Conclusively, purinergic signaling activated Erk1/2 signaling cascades play an essential role in the shock wave treatment induced proliferative and wound healing effect. The thereby broadened knowledge on the underlying mechanistic principles of the effect of shock wave treatment contributes to the establishment of shock wave therapy as a feasible standard treatment for soft tissue wound healing disorders such as diabetic or chronic wounds.
There is critical unmet need for new vascularized tissues to support or replace injured tissues and organs. Various synthetic and natural materials were already established for use of two-dimensional (2D) and three-dimensional (3D) in vitro neovascularization assays, however, they still cannot mimic the complex functions of the sum of the extracellular matrix (ECM) in native intact tissue. Currently, this issue is only addressed by artificial products such as Matrigel™, which comprises a complex mixture of ECM proteins, extracted from animal tumor tissue. Despite its outstanding bioactivity, the isolation from tumor tissue hinders its translation into clinical applications. Since nonhuman ECM proteins may cause immune reactions, as are frequently observed in clinical trials, human ECM proteins represent the best option when aiming for clinical applications. Here, we describe an effective method of isolating a human placenta substrate (hpS) that induces the spontaneous formation of an interconnected network of green fluorescence-labeled human umbilical vein endothelial cells (gfpHUVECs) in vitro. The substrate was biochemically characterized by using a combination of bicinchoninic acid (BCA) assay, DNA, and glycosaminoglycan (GAG) content assays, sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) analysis and Western blot, angiogenesis arrays, chromatographic thrombin detection, high performance liquid chromatography (HPLC)-based amino acid quantification analysis, and assessment of antimicrobial properties. 2D in vitro cell culture experiments have been performed to determine the vasculogenic potential of hpS, which demonstrated that cell networks developed on hpS show a significantly higher degree of complexity (number of tubules/junctions; total/mean tube length) when compared with Matrigel. As 3D cell culture techniques represent a more accurate representation of the in vivo condition, the substrate was 3D solidified using various natural polymers. 3D in vitro vasculogenesis assays have been performed by seeding gfpHUVECs in an hpS-fibrinogen clot. In conclusion, hpS provides a potent human/material-based alternative to xenogenic-material-based biomaterials for vascularization strategies in tissue engineering.